The following description is used to describe the background and products, materials and production methods that may comprise specific parts of preferred embodiments in the disclosure of this disclosure.
The majority of all laminate floors are produced according to a production method generally referred to as Direct Pressed Laminate (DPL). Such laminated floors have a core of 6-12 mm fibreboard, a 0.2 mm thick upper decorative surface layer of laminate and a 0.1-0.2 mm thick lower balancing layer.
The surface layer of a laminate floor is characterized in that the decorative and wear properties are generally obtained with two separate layers of paper, one above the other. The decorative layer is generally a melamine formaldehyde (hereafter shortened to melamine) impregnated printed paper and the wear layer is a melamine impregnated transparent overlay paper, which comprises small wear resistant aluminium oxide particles such as corundum, hereafter shortened to aluminium oxide.
The overlay paper is made of pure cellulose, which is based on delignified pulp. The overlay paper becomes almost completely transparent after lamination and the appearance of the decor paper is visible. Thicker overlay papers with a considerable amount of aluminium oxide particles may give a high wear resistance. The disadvantage is that they are less transparent and a grey layer that disturbs the printed pattern covers the decorative pattern.
The wear resistant aluminium oxide particles may be included in an overlay paper in several ways during impregnation. They may be mixed into the liquid melamine resin or scattered on the wet overlay paper. Paper based overlay may be replaced with a liquid overlay comprising a mix of aluminium oxide particles and liquid melamine resin that is applied on the impregnated décor paper.
The printed decorative paper and the overlay are laminated to a HDF core in large discontinuous or continuous laminate presses where the resin cures under high heat (about 170° C.) and pressure (40-60 bars) and the papers are laminated to the core material. An embossed press plate or steal belt forms the surface structure. Sometimes a structured paper is used as a press matrix. The embossing is in high quality floors made in register with the design.
Laminated floors may also be produced with direct printing technology. Hydro printing inks are used to print the décor by a multicolour printing press. The print is covered with a protective transparent wear layer that may be an overlay, a plastic foil or a lacquer that may comprise wear resistant particles.
Direct printing technology may be replaced with digital printing technology that is much more flexible and small production volumes can be economically manufactured. The difference between these two methods is mainly the printing step where the printing rollers are replaced by a digital non-contact printing process.
Recently new “paper free” floor types have been developed with solid surfaces comprising a substantially homogenous powder mix of fibres, binders and wear resistant particles hereafter referred to as WFF (Wood Fibre Floor).
The powder mix may comprise aluminium oxide particles, melamine resins and wood fibres. In most applications colour pigments are included in the mix and all these materials are applied in dry form as a mixed powder on a HDF core and cured under heat and pressure to a 0.1-1.0 mm solid layer.
Several advantages over known technology and especially over conventional laminate floorings may be obtained such as increased wear and impact resistance, deep embossing, increased production flexibility and lower costs. Digital powder printing has been developed and it is possible to create very advanced designs by injecting ink into the powder prior to pressing. The powder layer may include one or several powder based base colours and digital ink jet printing may only produce a small part of the total décor. A powder overlay comprising a mix of transparent fibres, wear resistant particles and melamine powder may be used to increase the wear resistance of the digital print. Such protective layer is applied even on the base layer where it is not needed since abase layer comprising wear resistant particles have sufficient wear resistance.
Wood floors are delivered as pre finished floors with a wood surface that is coated with several transparent layers in the factory. The coating may be made with UV cured polyurethane that comprises wear restante particles.
Ceramic tiles are one of the major materials used for flooring and wall coverings. A tile body comprising clay minerals is covered with one or several layers of glaze that may comprise wear resistant particles.
Luxury Vinyl Tiles, generally referred to as LVT floorings, are constructed as a layered product. The base layer is made primarily of PVC mixed with chalk filler in order to reduce material costs. The base layer has a high quality printed decorative PVC foil on the upper side. A transparent wear layer of vinyl with a thickness of 0.2-0.6 mm is generally applied on the decorative foil. The transparent layer may include a coating of polyurethane, which provides additional wear and stain resistance. Such polyurethane layer may comprise wear resistant particles.
As a summary it may be mentioned that wear resistant particles, especially aluminium oxide, are used in many floor types in order to increase the wear resistance of the floor surface.